Statistical Analysis of the Reproducibility of the Intravenous Glucose Tolerance Test and the Serum Insulin Response to This Test in Middle-Aged Men

Abstract

The reproducibility of the intravenous glucose tolerance test (IVGTT) and the serum insulin response to this test have been studied in 48 healthy middleaged men participating in a health screening program. Two tests were done 4–6 weeks apart. The subjects were ambulatory, and no diet prescriptions other than recommendation of an overnight fast were given. Under these circumstances the correlation between the K values of the two tests was low (r=0.55), and the equation for linear regression was y=0.56x+0.61. The intraindividual variation was 21 per cent, expressed as the coefficient of variation. The early increases in glucose-stimulated serum insulin concentrations in the two tests were significantly correlated (r=0.87), and this equation for linear regression was y=0.81x+10. The coefficient of variation intraindividually for this determination was 20 per cent. We conclude that the K values of the IVGTTs must be judged with caution when obtained in ambulatory practice, especially when the result is used for preventive measures and long-term follow-up of asymptomatic individuals.

Key Words:

• Health screening
• insulin
• K value
• serum